Normally, it is not recommended to abandon the heavyweights who carried your team to the fantasy playoffs. Normally, the Tracker would not suggest you sit your stalwarts.

But this week, we’re going to do at running back what Jim Harbaugh did at QB this season with the 49ers — sit someone who has led the team to success in favor of an unproven option.

Ahmad Bradshaw (knee) is banged up, again. Stevan Ridley will have a tough time finding running lanes against the 49ers’ league-leading run defense. C.J. Spiller could have a rough afternoon vs. the stingy Seahawks. Not ready to trust DeMarco Murray?

These are hard questions, which require difficult answers. Murray has yet to look fully healthy after a foot injury and faces the stiff Steelers run defense. The consistent output of Ridley and Spiller make them more comfortable starts, but they don’t have desirable matchups.

Ryan Mathews, on the other hand, has been fantasy poison. His career has been pockmarked by injury (he missed the first two games this season), and when on the field he has yet to perform like a top-tier RB — he has just one game this season that has produced more the eight fantasy points.

But this week he gets the Panthers, who have allowed double-digit fantasy output by opposing RBs in every game but one this season, and more than 20 five times.

Don’t have Mathews as an option, and forced to scour the waiver wire? Perhaps David Wilson still is available. With Bradshaw out and backup Andre Brown (leg) on IR, Wilson will get a heavy does of carries this week, coming off his Week 14 breakout against the Saints.

Start Mathews over any of the aforementioned, and play Wilson instead of Murray, but not Ridley or Spiller.

BIG WEEKS

Russell Wilson, QB, Seahawks, at Bills

After struggling on the road early in the season, the rookie has gotten better in each of his past three road trips. Bills rank 25th in fantasy points allowed to opposing QBs.

Wes Welker, WR, Patriots, vs. 49ers

Rams WR Danny Amendola, the oft-injured Wes Welker of the Midwest, racked up 102 yards on 11 catches Week 10 against the 49ers — and had an 80-yard catch negated by a penalty. The Real Welker has a better QB.

Brandon Myers, TE, Raiders, vs. Chiefs

Has four TD catches in past six games, and since Week 8 has been off one week, on the next. Was a no-show vs. the Broncos, four days after an 130-yard outing vs. the Browns, so he’s due.

Lions, DEF/ST, at Cardinals

You can’t expect the Cardinals to play as poorly as last week, when the Seattle DEF/ST racked up two scores, eight turnovers and three sacks. But even half of that is a great fantasy day for a defense.

SMALL WEAKS

Matthew Stafford, QB, Lions, at Cardinals

Arizona showed last week it doesn’t need the opposing quarterback to have a big day in order to get blown out. The Cardinals have given up more than one passing touchdown just four times in 13 games.

James Jones, WR, Packers, at Bears

We’re not ready to dismiss the Chicago defense, despite a rash of injuries. Eventually Greg Jennings, who has been back two weeks, will reclaim his top-target status — maybe this week.

Jason Witten, TE, Cowboys, vs. Steelers

Steelers have allowed just one TD by a TE in past nine games, and no double-digit fantasy totals since Week 3. Witten has just one TD this year, way back in week 4.

49ers, DEF/ST, at Patriots

Defenses just don’t score against the Pats. In ESPN’s basic scoring leagues, which use sliding points-allowed scale, opposing defenses have total minus-19 for the season.

The Decision

Drew Loftis and Anthony Sulla-Heffinger tell you who you should start:

JOSH FREEMAN vs. CAM NEWTON

Drew: Freeman — Newton has been unstoppable for the past five weeks, and there is no reason to suspect he will flounder vs. the Chargers, but I’m going to lean Freeman based on the matchup vs. the awful Saints defense. He racked up 420 yards and three TDs in first meeting in Week 7.

Anthony: Newton — There’s no denying Freeman had success against the porous Saints secondary, but Newton is as locked in as you can get right now. The Chargers have a good defense against the run, but are almost as bad as the Saints when it comes to defending the pass (24 TDs this season), and Newton hasn’t thrown an INT in four weeks, meaning he’s just as big of a threat passing as he is on the ground.